is in Kiwi3D possible to model Truss elements, or beams with rotational freedom in the main 3 directions / hinges?
I see some CF/Coupling feature on the Beam command but it is not clear. Shuold I use the CPA? Strange…
I want to model somehow Truss elements (0 Moments at the ends).
yes. Just use a cable element and set the refinement to P=U=1 (recommended). It would be also possible by setting 2 hinges at the end of a beam by setting HA and HE to true (hinge at start and end point, see also the documentation). But this has the disadvantage that the beam can rotate around its own axis and is not statically determined; so a torsional support is needed. And a beam is computationally more expensive than the cable/truss.
coupling features are only to be used to control the automated coupling. By default, Kiwi couples all elements that do intersect. This behavior can be manipulated by the coupling features. CPA can by used for setting scissor joints.
If you want to have a full hinge, you can use HA and HE input. If only certain directions should be released, you have to put a full hinge as well + the cpa component with the axis it should be able to rotate around.